HomeMy WebLinkAboutDrainage Reports - 11/01/1983GOLDEN MEADOWS 4th FILING
FINAL DRAINAGE REPORT
MEDEMA HOMES, INC.
NOVEMBER 1983
TARANTO
STANTON
& TAGGE
CONSULTING
ENGINEERS
1
1
' TARANTO
STANTON
'& TAGGE
CONSULTING ENGINEERS
City of Fort Collins
' Department of Engineering
Drainage
P.O. Box 580
' Fort Collins, CO 80522
Attn: Mr. Phil Waite
November 14, 1983
Re: Golden Meadows 4t1i Filing
Job No. 317-000.
Dear Phil:
Attached please find our final drainage study for Golden Meadows 4th
Filing. This study has been prepared in conjunction with other studies
prepared for this and surrounding areas.
' If you have any questions, please contact our office.
' Respectf lly ubmit ,
Robert H. Schemmerlin , P.E.
TARANTO, STANTON & T
CONSULTING ENGINEERS
RHS:lgc
1
t 1
' 112 W, 11TH AVE.
HOLDREGE, NE68949
(308) 995-6677
6412 S. COLLEGE AVE.
FORT COLLINS, CO 80525
(303) 226-0557
INTRODUCTION
Golden Meadows Filing No. 4 subdivision consists of 28.5 acres located in
Section 31, Township 7 North, Range 68 West of the 6th Principal Meridian,
City of Fort Collins, Colorado. It is bounded on the west and north by
Golden Meadows Filing No. 2 and 3, the east by McMurray Drive, and on the
south by Golden Meadows Filing No. 5 and Wheaton Drive. No off -site
drainage enters this project. Part of the Dixon Canvon Lateral Irrigation
Ditch bounds a portion of this parcel to the northeast., The drainage map
for this site is located with the construction drawings.
CRITERIA
This report has been prepared using the City of Fort Collins storm drainage
criteria. Because this site is under 200 acres, the rational formula
Q = c cf i A was used to determine site runoffs. In addition, storm
drainage and inlet sizing were determined in accordance with the methods
and reduction factors set forth in these criteria. For this project, the 2
year and 100 year frequency storms were calculated for undeveloped and
developed conditions. The following values were used for design purposes:
C undeveloped = 0.2
C developed = 0.6
Cf 2 year storm = 1.00.
.Cf 100 year storm = 1.25
All calculation sheets are included in this report under Appendix "A".
UNDEVELOPED CONDITIONS
The site drains- west to east and has at least one depressed area where
drainage has no outfall. The majority of undeveloped flow enters the Dixon
Canyon Irrigation Ditch by draining over land at slopes generally under 1
percent. The 2 and 100 year frequency storms were calculated as follows:
Q2 = 4.6 cfs
Q100 17.1 cfs
DEVELOPED CUMITIONS
As can be seen on the
developed
site drainage map, the
proposed site is
divided into 9 drainage
basins. Basins 1 thru 7 and 9 drain on site, in
storm drains, and curb
and gutter
into a detention pond
at the southeast
corner of this property. Area 8
drains directly into
the Dixon Canyon
Irrigation Ditch. The
developed
flow from Area 8 is
much less than
historical flows and will enter the ditch as sheet flow, and therefore,
will not be a hazard to the ditch. .
Due to curb and gutter capacity requirements, it is necessary to provide a
storm drain system to pick up the 2 year developed flows at selected points
throughout the site. This storm drain is shown in the construction
drawings and on the drainage map. Water gets to the storm drain in
rollover type curb and gutter. Capacity calculations of the curb and
gutter meet the requirements of the Fort Collins drainage criteria and are
not exceeded. Flows in the storm drain are controlled by size and.slope of
the pipe. Inlet size at all locations will therefore be the 4' minimum
required by the City's drainage criteria.
Curb and gutter capacities for 2 year and 100 year floods can be. seen on
the table shown in Appendix "A". All capacities shown on this table are
for h streets. It is seen that although storm sewer is required to handle
2 year floods, 100 year flows are easily handled in the proposed curb and
gutter sections from the top of the site to the detention pond:
After entering the on -site storm wa4r detention pond, floods are
transferred t9 they larger. Collindale detention pond via a I
- , drain. The design for
this storm drain ; o p -- i a
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AND CGNSj7Z.�GT2D ®c2to2 Tn T}te cDW',M�c-7LeW or-1l1¢
r-w_-�T UNti•
According to the design, this drain is capable of handling -27 efs. This is
lower than the incoming 100 year flood, but the on -site detention pond has
the storage to detain the 100 year flows through the .storm design period.
We have calculated a required detention of 2.9 acre/feet.. This is less
than .the 3.0 acre/feet calculated to be available. The mass flow diagram
which depicts the detention required is. shown.in,Appendix "A^.
A swale is required between Lots 14 and 15, block 41 to carry the 100-year
i
flows from Cape Cod Circle to the detention pond. A 30-foot drainage and
utility easement is provided for this purpose and.is shown on the drainage
map. The contours depicting this Swale, as well as,a sectional view of the
swale showing the high. water elevation is also shown on .this map. The
.. calculations which generated this design are in Appendix
A summary of the developed drainage. calculations are shown in Table A as
well as sizing data for storm drains and inlets.. No adverse drainage
conditions are expected to be created by the development of this project.
In conclusion, the final drainage developed from ,this project will .create
minimal damage to property in the event of a major storm. If you have any .
questions, please contact our office.
After entering the on -site storm water detention pond, floods are
transferred to the larger Collindale detention pond via a outfall
storm 30" drain. The design for this strom drain is to involve some
temporary flow restriction and will be finalized and constructed
prior to the construction of the first unit.
According to the design, this drain is capable of handling 22 cfs. This is
lower than the incoming 100 year flood, but the on -site detention pond has
the storage to detain the 100 year flows through the storm design period.
We have
calculated a required detention
of 2.9 acre/feet.
This
is less
than the
3.0 acre/feet calculated to be
available. The mass
flow
diagram
which depicts the detention required is shown'in Appendix "A".
A swale is required between Lots 14 and 15, block 4, to carry the 100-year
flows from Cape Cod Circle to the detention pond. .A 30-foot drainage and
utility easement is provided for this purpose and is shown on the drainage
map. The contours depicting this Swale as well as a sectional view of the
swale showing the high water elevation is also shown on this map. The
calculations which generated this design are in Appendix "A"..
A summary of the developed drainage calculations are shown in Table A as
well. as sizing data for storm drains and inlets. No adverse drainage
conditions are expected to be created by the development of.this.project.
In conclusion, the final drainage developed from this project will create
minimal damage to property in the event of a major storm. If you have any
questions, please contact our office.
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APPENDIX "A"
CLIENT � i *=('c.- (f f-. •-^fr c ^ - .. - JOB NO. -
PROJECT n '�4: '-� '., `�� ]'- CALCULATIONS FOR ii�_Y fIR�•�
TARANTO
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TARANTO
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-29-
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